Method of fabricating arrays of individually oriented micro mirrors for use in imaging security devices

Abstract

A visual display assembly useful as an authentication or anti-counterfeiting element. The assembly includes a substrate and, on a surface of the substrate, an array of micro mirrors receiving ambient light. Each mirror includes a reflective surface to reflect the ambient light to display an image that appears to float in a plane, which is spaced a distance apart from the surface of the substrate. The image includes a plurality of pixels, and the array of micro mirrors includes for each of the pixels a set of the micro mirrors each having a reflective surface oriented to reflect the ambient light toward a point on the plane corresponding to one of the pixels. Each of the sets of the micro mirrors includes a plurality of the micro mirrors, and the reflected ambient light each set of micro mirrors intersects to illuminate or write a pixel of an image.

We claim: 
     
       1. A method of fabricating a security element, comprising:
 assigning a first object in a starting digital image to a first image display plane and a second object in the starting digital image to a second image display plane; 
 with a processor of a computing device, executing code to provide an array design module that operates to select a set of micro mirrors in an array of the micro mirrors to display each of the pixels of the first object in the first image display plane and to display each of the pixels of the second object in the second image display plane; 
 for each of the pixels, determining with the array design module an angular orientation of each of the micro mirrors in the selected sets of the micro mirrors; 
 generating a design output file including the angular orientation and location coordinates in the array for each of the micro mirrors in the selected sets of the micro mirrors; and 
 forming the array of the micro mirrors according to the design output file. 
 
     
     
       2. The method of  claim 1 , wherein the angular orientation is defined by coordinates of a normal vector from a reflective surface of each of the micro mirrors directing light to one of the pixels. 
     
     
       3. The method of  claim 1  wherein each of the sets of micro mirrors are selected randomly from a plurality of the micro mirrors located in a base of a cone on a surface containing the array of micro mirrors. 
     
     
       4. The method of  claim 3 , wherein the cone has an apex coinciding with coordinates of one of the pixels on the first or second image display planes. 
     
     
       5. The method of  claim 1 , wherein the angular orientations are calculated based on heights of the first and second image display. 
     
     
       6. The method of  claim 1 , wherein the angular orientations are calculated to provide a predefined angular offset of at least 10 degrees between the first and second image display planes. 
     
     
       7. A method of fabricating a security element, comprising:
 with a processor of a computing device, executing code to provide an array design module configured to select a set of micro mirrors in an array of the micro mirrors to display pixels of a first object in a first image display plane and to display pixels of a second object in a second image display plane spaced apart from the first image display plane; 
 for each of the pixels, determining, with the array design module, an angular orientation of each of the micro mirrors in the selected sets of the micro mirrors; 
 generating a design output file including the angular orientation and location coordinates in the array for each of the micro mirrors in the selected sets of the micro mirrors, wherein each of the sets of micro mirrors are selected randomly from a plurality of the micro mirrors located in a base of a cone on a surface containing the array of the micro mirrors; and 
 forming the array of the micro mirrors according to the design output file. 
 
     
     
       8. The method of  claim 7 , wherein the cone has an apex coinciding with coordinates of one of the pixels on the first or second image display planes. 
     
     
       9. The method of  claim 7 , wherein the angular orientation is defined by coordinates of a normal vector from a reflective surface of each of the micro mirrors directing light to one of the pixels. 
     
     
       10. The method of  claim 7 , wherein the angular orientations are calculated based on heights of the first and second image display. 
     
     
       11. The method of  claim 7 , wherein the angular orientations are calculated to provide a predefined angular offset of at least 10 degrees between the first and second image display planes. 
     
     
       12. A method of fabricating a security element useful on paper and coin currency and on product labels, comprising:
 with a processor of a computing device, executing code to provide an array design module configured to define an array of micro mirrors to be formed on a surface of a substrate; 
 generating a design output file including an angular orientation and location coordinates in the array for each of the micro mirrors; and 
 forming the array of micro mirrors according to the design output file, 
 wherein the array of micro mirrors is configured, when formed on the surface of the substrate, for receiving ambient light and, in response, displaying an image in a plane spaced a distance apart from the surface of the substrate, 
 wherein the image comprises a plurality of pixels, and 
 wherein the array of micro mirrors includes for each of the pixels a different set of the micro mirrors each having a reflective surface oriented, in a fixed manner, with a body of each of the micro mirrors rotated about at least one of first and second rotation axes extending through the body, to reflect the ambient light toward a point on the plane corresponding to one of the pixels. 
 
     
     
       13. The method of  claim 12 , wherein a voxel is created at each of the point on the plane via intersection of two or more beams of the reflected ambient light, and wherein each of the created voxels produces an effect of a point source of light floating above the surface of the substrate in the plane. 
     
     
       14. The method of  claim 12 , wherein each of the different sets concurrently reflect the ambient light to concurrently generate the plurality of pixels. 
     
     
       15. The method of  claim 12 , further comprising providing the substrate and forming the array of micro mirrors by casting the micro mirrors with a mirror tool in contact with the surface of the substrate. 
     
     
       16. The method of  claim 15 , wherein the substrate provided in the providing step comprises a clear, energy-cured polymer. 
     
     
       17. The method of  claim 12 , further comprising providing the substrate and forming the array of micro mirrors by metallization of surfaces of the micro mirrors, wherein the metallization applies a layer of aluminum, gold, or silver to form reflective surfaces. 
     
     
       18. The method of  claim 17 , wherein the forming the array of micro mirrors includes, prior to the metallization of the surfaces of the micro mirrors, embossing the surface of the substrate to form the surfaces of the micro mirrors and wherein the surface of the substrate includes an embossable coating or layer. 
     
     
       19. The method of  claim 12 , further comprising providing the substrate and forming the array of micro mirrors by filling in recessed surfaces associated with the micro mirrors with a filler comprising at least one of an ultraviolet (UV) varnish, an e-beam solvent, and a water-based varnish. 
     
     
       20. The method of  claim 19 , wherein the filler has a refractive index of at least 1.55, whereby at least a portion of the received ambient light at extreme angles is reflected to sharpen the displayed image.